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From "Hiller, Dean" <>
Subject (better info)any way to get the #writes/second, reads per second
Date Mon, 13 May 2013 17:06:47 GMT
Ah, okay iostat -x NEEDS a number like "iostat -x 5" works better(first
one always shows 4% util while second one shows 100%).  Iotop seems a bit
better here.

So we know that since we added our new node, we are slammed with read and
no one is running compations according to "clush -g datanodes nodetool

Any reason why cassandra might be reading a lot from the data disks(not
the commit log disk) more than usual?


On 5/13/13 10:46 AM, "Hiller, Dean" <> wrote:

>We running a pretty consistent load on our cluster and added a new node
>to a 6 node cluster Friday(QA worked great, but production not so much).
>One mistake that was made was starting up the new node, then disabling
>the firewall :( which allowed nodes to discover it BEFORE the node
>bootstrapped itself.  We shutdown the node and booted him up and he
>bootstrapped himself streaming all the data in.
>After that though, all the ndoes have really really high load numbers
>now.  We are trying to figure out what is going on still.
>Is there any way to get the number of reads/second and writes/second
>through JMX or something?  The only way I can see of on doing this is
>manually calculating it by timing the read count and dividing by my
>manual stop watches start/stop times(timerange).
>Also, while my load is load average: 20.31, 19.10, 19.72 , what does a
>normal iostat look like?  My iostat await time is 13.66 ms which I think
>is kind of bad, but not that bad to cause a load of 20.31?
>Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s
>avgrq-sz avgqu-sz   await  svctm  %util
>sda               0.02     0.07   11.70    1.96  1353.67   702.88
>150.58     0.19   13.66   3.61   4.93
>sdb               0.00     0.02    0.11    0.46    20.72    97.54
>206.70     0.00    1.33   0.67   0.04

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